Abstract: To optimize the extraction technology and study antioxidant activity of polysaccharide from coffee flower (ACP), ultrasonic temperature, ultrasonic time, ratio of fluid-solid, ultrasonic power, sample immersion time and volume percentage of ethanol were investigated by using polysaccharide extraction yield as indicator. Then ultrasonic temperature, ultrasonic time and ultrasonic power were used as mainly influence factors, the extraction technology was optimized by response surface method. Antioxidant activity of ACP was investigated by DPPH· and ABTS⁺· scavenging effects, and FRAP assays. The results demonstrated that the ultrasonic extraction optimum technological conditions were: Ultrasonic temperature 69.5 ℃, ultrasonic time 93 min, ultrasonic power 175 W, ratio of fluid-solid 10:1 mL/g, sample immersion time 30 min, and volume percentage of ethanol 80%. Under the the yield of polysaccharides was 2.292%. The results indicated that the value of IC₅₀ based on DPPH· scavenging effect of ACP was 3.844 mg·mL⁻¹, the ABTS⁺· scavenging activity was 0.921 mmol Trolox/g ACP. The FRAP values of ACP by FRAP assay was 0.0565 mmol Fe²⁺/g ACP, which showed that ACP had weak antioxidant activity. This study would provide a theoretical basis for the comprehensive utilization and development of coffee by-products.